Saxon » SaxonJS

https://www.w3.org/TR/xslt-30/#result-document-restrictions says (emphasis added by me):

There are restrictions on the use of the xsl:result-document instruction, designed to ensure that the results are fully interoperable even when processors optimize the sequence in which instructions are evaluated. Informally, the restriction is that the xsl:result-document instruction can only be used while writing a final result tree, not while writing to a temporary tree or a sequence. This restriction is defined formally as follows.

[Definition: Each instruction in the stylesheet is evaluated in one of two possible output states: final output state or temporary output state ].

[Definition: The first of the two output states is called final output state. This state applies when instructions are writing to a final result tree.]

[Definition: The second of the two output states is called temporary output state. This state applies when instructions are writing to a temporary tree or any other non-final destination.]

The instructions in the initial named template are evaluated in final output state. An instruction is evaluated in the same output state as its calling instruction, except that xsl:variable, xsl:param, xsl:with-param, xsl:function, xsl:key, xsl:sort, xsl:accumulator-rule, and xsl:merge-key always evaluate the instructions in their contained sequence constructor in temporary output state .

[ERR XTDE1480] It is a dynamic error to evaluate the xsl:result-document instruction in temporary output state .

However, when reading through the SaxonJS 3 documentation about many ixsl extension functions like https://www.saxonica.com/saxonjs/documentation3/index.html#!ixsl-extension/functions/doc, I find usages like

Asynchronously fetch an XML document, proceeding when the document is available:

  <xsl:template name="xsl:initial-template">
    <ixsl:promise select="ixsl:doc($href)"
      on-completion="f:go#1"/>
  </xsl:template>
  
  <xsl:function name="f:go" ixsl:updating="true">
    <xsl:param name="doc" as="document-node()"/>
    <xsl:result-document href="{$output-file}">
      <xsl:copy-of select="$doc"/>
    </xsl:result-document>
  </xsl:function>

Is the ixsl:updating decisive here to allow the use of xsl:result-document in an xsl:function with SaxonJS 3?